In solid state physics, a general constitutive tensor \(\chi ^{ijkl}\)  includes the full set of 36 independent components. In \((1+3)\) -splitting form, it is represented as [1]}
\(\chi ^{ijkl}=\left( \begin{array}{cc}\epsilon ^{\alpha \beta } & \gamma ^\alpha {}_\beta \\\tilde{\gamma }^\alpha {}_\beta &\pi _{\alpha \beta }\end{array} \right)\,.\) 
